Help with tables

So I have a function for creating text with sprites (I'm sure people have done this already, but i specifically want help with one thing):

charspr{74,75,76,77,78,79,90,91,92,93,94,95,106,107,108,109,110,111,122,123,124,125,126,127,138,139,140,141,142,143,154,155,156,157,158,159,170,171,172,173,174,175,186,187,188}
charname{"a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","0","p","q","r","s","t","u","v","w","x","y","z",".","-","!","\"","\'",",",":",";","𝘹","?","1","2","3","4","5","6","7","8","9"," "}

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I'm not entirely sure if this is bug or my mistake, but i can't figure it out.
Basicly I have code that should save what I'm typing (it's the last line) to a var named code.
However if i add a function for deletion it doesn't work properly:
I can still type, however i have to hold for few seconds before it registers key presses, which does not apply for the backspace.
I also figured out, that only the first code will work properly, meaning if i swap the if with the var set, only typing works.

 if stat(31)=="\b" then
   code=sub(code,0,-2)
 end
 code=code..stat(31)

I'd be really happy to know if it's my mistake or a bug.